Reactivation/Acceleration of Landslides Caused by the 2018 Baige Landslide-Dammed Lake and its Breach Floods Revealed by InSAR and Optical Images

Landslide-dammed lakes and their breaches can reactivate/accelerate landslides, causing potential damages. However, in the absence of displacement observations, the spatial-temporal deformation patterns of the landslide-dammed lakes and associated floods reactivated/accelerated landslides remain underexplored. In this article, we use the 2018 Baige landslide-dammed lake and associated floods reactivated/accelerated landslides to investigate the behaviors of such landslides. We first use an improved interferograms Stacking method to detect landslides, then utilize the multitemporal interferometric synthetic aperture radar to derive their deformation history. Through retrospective analysis of the deformation history and optical images, we find that the water level fluctuations and floods caused by the Baige landslide-dammed lake and its breaches reactivated/accelerated six landslides upstream and five landslides downstream. The area of the largest reactivated/accelerated landslide is about 5 km². The maximum velocity change of these reactivated/accelerated landslides is about 20 cm/year. Landslide reactivation/acceleration occurs progressively from the toe to head, resulting in varying reactivation/acceleration times for different parts. The velocity change and acceleration area have a linear relationship, with larger landslides showing larger velocity changes and prolonged activity than smaller ones. Among these 11 reactivated/accelerated landslides, 4 are located in the river narrow sections and their volumes are all larger than that of the Baige landslide. Thus, their failure may cause larger damages than that caused by the Baige landslide. Our findings contribute to a better understanding of landslide-induced geological hazard chains and landslide behaviors.